The invention relates generally to the servicing of valves and specifically to a tool and method for the extraction of press-fitted seats from the seat recesses of a valve.
Heretofore, tools have been employed to remove valve seats from recesses in a flowline. However, such tools have normally employed means to grip or bite into the seats with a force being applied to the gripping means to remove the valve seat from the recess. The tools have been operated heretofore both manually and by pressurized fluid.
Particularly after valves have been employed in service with corrosive fluids in the flow passages, the seats become firmly positioned in recesses and are difficult to dislodge. The gripping means heretofore have normally employed teeth or some other means which are imbedded in the seats for removal of the seats and at times when the seats are tightly fitted in the recesses, the teeth will gouge or shear off the metal adjacent the imbedded area and thereby be removed from engagement with the seats. The teeth then have to be reengaged with the seats for removal.
An example of an extraction tool employing gripping means to engage an annular seat is illustrated in U.S. Pat. No. 3,296,687 dated Jan. 10, 1967 and shows teeth which imbed themselves in the seat and then fluid pressure is employed to urge the teeth outwardly for pulling the seat from the recess. As noted above, particularly when the seat is firmly embedded in the recess which might occur after prolonged use with corrosive fluids in the flow passage, the teeth will somtimes slip off the seat before the seat is dislodged from the recess. This sometimes necessitates several attempts in engaging the teeth with the seat before the seat is removed.